1. Field of the Invention
The present invention relates to control of a passenger protection system for protecting passengers in a car crash and, more particularly, a start controlling method for a passenger protection system and a start controlling system for a passenger protection system. Both are able to distinguish between a low speed crash and a soft crash, and a recording medium for recording a start controlling program for a passenger protection system.
2. Description of the Related Art
In the prior art, it has been well known that, according to the running speed and the crashed part of the vehicle, type of crash of the vehicle is classified into a low speed frontal crash wherein an entire frontal area of the vehicle collides with an object at low speed, a high speed frontal (head-on) crash wherein the entire frontal area of the vehicle collides with the object at high speed, a high speed offset crash wherein a part of the entire frontal area of the vehicle collides with the object at high speed, and others.
In a passenger protection system represented by an air bag system, for example, which can protect a body of the passenger in such crash, normally it is designed that such start control should be executed by taking account of difference in the acceleration of the vehicle in a crash from that in normal running. Various start controlling methods and systems for embodying the same, etc. have been proposed up to now.
A following concept has been proposed as one of start control concepts for the passenger protection system which has been proposed until now. In other words, at first the integral value (speed integral value) of the deceleration (so-called impact acceleration) upon crash is calculated. Then, it is decided whether or not change in the integral value within a predetermined range is continued over a predetermined period of time, i.e., it is decided whether or not stagnation of the integral value is caused. If it has been decided that the stagnation of the integral value is caused, a predetermined value is then added to the integral value. Therefore, the integrated value is advanced rather than the actual integral value, and then start of the air bag is carried out when it is decided that the integrated value has exceeded a predetermined threshold value.
In the meanwhile, while taking account of the stagnation of the speed integral value which is caused in the crash which is generally called as a soft crash such as an oblique crash, an offset crash, a pole crash, etc., the above start controlling method has been proposed to start the air bag without fail, while distinguishing between the soft crash and the high speed crash in which no stagnation of the speed integral value is caused, etc. However, such start controlling method has not been satisfactory in the following respects and therefore has not been employed in practical use.
More particularly, there has been the low speed crash as the case where start of the air bag is not needed. In such low speed crash, change in the speed integral value of the impact acceleration has the stagnation of the speed integral value, like the above-mentioned soft crash. In addition, sometimes a stagnation time of the speed integral value in the low speed crash is close to or resembles that that in the soft crash. Therefore, in some cases there has been a possibility that distinctions between the soft crash and the low speed crash become difficult to determine according to the above concept.